ABSTRACT Despite long-term combined antiretroviral therapy (cART), HIV+ drug abusers experience more severe and rapid progression of HIV-associated neurocognitive disorders (HAND). Methamphetamine (Meth) is a potent stimulant, which is highly abused in the USA, and associated with chronic systemic inflammation. Understanding the mechanism(s) by which Meth and HIV induce pathologies in the brain, whether and how chronic cART alters astrocyte/neuron function in the CNS, and whether Math (or other stimulants) affects cART, is critical for improving current, and developing new effective therapeutic strategies for treating Meth addiction and its comorbid conditions with HIV/AIDS. The medial prefrontal cortex (mPFC) is one of the key regulators of cognition and addiction; but it is profoundly altered following chronic Meth and HIV exposure in vivo with disrupted dopamine (DA) neurotransmission and immune activation of astrocytes. Both human and laboratory animal studies demonstrate that the mPFC dysregulation is significantly implicated in chronic Meth-induced brain dysfunction, associated with euphoria, craving, drug-taking and relapse. Cumulating evidence also indicates that both astrocytes and glutamatergic pyramidal neurons in the PFC are altered after chronic Meth or HIV exposure. Chronic Meth in vivo induces astrocytic and neuronal plasticity that differs from changes induced by acute Meth in vitro; but the underlying mechanism(s) of either one is not fully understood. In this proposed study, we will elucidate a novel, trace amine-associated receptor 1 (TAAR1)-mediated mechanism, by which acute Meth in vitro alters astrocyte activity; and determine alterations in this mechanism after Meth self-administration (Meth-SA) followed by a withdrawal (that elicits drug-seeking), in HIV-1 transgenic (Tg) or non-Tg rats. Moreover, we will also determine whether and how chronic cART in vivo affects functional activity of mPFC astrocytes and neurons; and whether such cART effects are altered by Meth-SA in the context of neuroHIV. Specifically, we will first define the mechanism by which chronic Meth in vivo alters astrocyte function (Aim1). We then will determine the mechanism by which Meth/HIV impacting on mPFC astrocytes/ neurons (Aim2). Finally, we will identify chronic effects of cART (using a fixed-dose combination of abacavir, dolutegravir and lamivudine) in vivo on mPFC astrocytes/neurons, and whether chronic Meth-SA alters them (Aim3). To prove the fundamental base of this proposed research, we provide justification, related citations, and preliminary data to support the Scientific Premise, Scientific Rigor, Relevant Biological Variables, and Resource Authentication for this proposal. Outcomes from the proposed research will reveal the novel, TAAR1- mediated mechanism that plays a key role in underlying the comorbid Meth/HIV impact, and chronic cART effects, on altering astrocytes and pyramidal neurons in the mPFC. This will advance our understanding for interactive effects of Meth, HIV and cART in the CNS, and therefore will induce a strong impact to the field.